Measured monopole and dipole room responses - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 14th June 2009, 06:17 PM   #1
Elias is offline Elias  Finland
diyAudio Member
 
Elias's Avatar
 
Join Date: May 2003
Location: Where you live
Default Measured monopole and dipole room responses

Hello,

I did some measurements with monopole and dipole bass in a room.

Particularly I try to pay attention to temporal behaviour since as I believe steady state measurements in this case are pretty useless when considering human perception. Also I try to match the measurement excitation signal to represent the final situation, that is music.

Music is no impulse nor steady state sinusoid, thus I'm using short tone bursts with shaped envelope. It will give quite good visuality to what is happening in the room due the reflections.

I plotted some spectrograms. Note the horisontal axis is the time in periods. Vertical axis is frequency.

Also note that each frequency the maximum value of the burst envelope is normalised to 0dB. In this way it is possible to compare the room responses in perceptual sense since each frequency the amplitude is the same.

To start here's the ideal case for a reference, response of a laptop soundcard:


- Elias
Attached Images
File Type: png soundcard_sg-norm.png (13.1 KB, 2305 views)
__________________
Liberate yourself from the illusion of two speaker stereo triangle
Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
  Reply With Quote
Old 14th June 2009, 06:22 PM   #2
Elias is offline Elias  Finland
diyAudio Member
 
Elias's Avatar
 
Join Date: May 2003
Location: Where you live
Here is the measured response of a H frame dipole. It has 2 12" elements. Measurement distance is about 1m and hight 1m.

Some room reflections are present:


- Elias
Attached Images
File Type: png hdipoli_sg-norm.png (13.9 KB, 2335 views)
__________________
Liberate yourself from the illusion of two speaker stereo triangle
Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
  Reply With Quote
Old 14th June 2009, 06:24 PM   #3
Elias is offline Elias  Finland
diyAudio Member
 
Elias's Avatar
 
Join Date: May 2003
Location: Where you live
And here is the measured response of the monopole. It has one 12" element in 100 litres closed enclosure.

The room response looks pretty messy:


- Elias
Attached Images
File Type: png monopoli_sg-norm.png (14.7 KB, 2271 views)
__________________
Liberate yourself from the illusion of two speaker stereo triangle
Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
  Reply With Quote
Old 14th June 2009, 06:42 PM   #4
Elias is offline Elias  Finland
diyAudio Member
 
Elias's Avatar
 
Join Date: May 2003
Location: Where you live
From these measurements it can be said that in the case of the dipole the time the envelope maximum occurs follows quite well the original envelope, but in the case of the monopole the envelope maximum occurs in almost a randomly manner. With monopole at some freqs the envelope maximum and thus the energy that reaches the listener is delayed - it has a poor energy delay (if one not like to use the term group delay).

Is this a reason for a perceived 'slow bass'? In this sense the dipole is 'faster' - the energy delay is smaller.

The beauty of using this excitation signal is you can listen how the room sounds like while doing the measurement. I can state that comparing dipole and monopole in this room one can hear big difference. I think in this case the visualisation yields the same result as the ear hears: In the case of the dipole the bass notes are clearly separated and it is easy to follw the bass line, whereas in the case of the monopole the bass sounds like it's never going to die out and the bass line is mudded.


- Elias
__________________
Liberate yourself from the illusion of two speaker stereo triangle
Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
  Reply With Quote
Old 14th June 2009, 07:07 PM   #5
diyAudio Member
 
Join Date: Sep 2008
Great to see some measurements.

However -10dB is not that interesting as "direct sound" is what you mostly get. -40dB is a lot more useful. -60dB even more so. RT60 and all.

10ms is only 3,4m so you can't really tell me that you are showing any "in room" response.
  Reply With Quote
Old 14th June 2009, 07:37 PM   #6
Elias is offline Elias  Finland
diyAudio Member
 
Elias's Avatar
 
Join Date: May 2003
Location: Where you live
Hello,

Quote:
Originally posted by David_Web
However -10dB is not that interesting as "direct sound" is what you mostly get. -40dB is a lot more useful. -60dB even more so. RT60 and all.

10ms is only 3,4m so you can't really tell me that you are showing any "in room" response.
Take a another look at equal loudness contours at bass frequencies. 10dB is a huge perceived difference. 60dB dynamic range at bass in a small room is a wishfull thinking only - the signal has to go above pain level to achieve that.

And I think RT60 is not much of a use in small rooms.

Note again that the time axis is in periods, not linear time!

- Elias
__________________
Liberate yourself from the illusion of two speaker stereo triangle
Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
  Reply With Quote
Old 14th June 2009, 07:58 PM   #7
diyAudio Member
 
Join Date: Sep 2008
Sorry. I must really be slipping. I reread your post before and didn't see it. Got it now.

Would it be possible to see the graphs in ms?
I find it hard to translate to cycles as time matters to me.
  Reply With Quote
Old 14th June 2009, 09:01 PM   #8
Elias is offline Elias  Finland
diyAudio Member
 
Elias's Avatar
 
Join Date: May 2003
Location: Where you live
Quote:
Originally posted by David_Web
I find it hard to translate to cycles as time matters to me.

That's just the key! One needs to get rid of the traditional idea of having looking the room in linear time. For a human linear time have little perceived importance at different frequencies.

For example, take a 10ms reflection: At 20Hz it would be very hard to detect by ear as one period of 20Hz is already 50ms. But at 20kHz (one period is only 50us) 10ms reflection should be easily detectable by the ear.

Thus it is better, in my opinion, to scale the time axis to the frequency in question one is making the observation.

Keep the end user in mind!

- Elias
__________________
Liberate yourself from the illusion of two speaker stereo triangle
Dipole Bass vs Monopole Bass Stereophonic Sound from a Single Loudspeaker 3 Speaker Linear Stereo Matrix Wavelets
  Reply With Quote
Old 17th June 2009, 11:25 PM   #9
jeepee is offline jeepee  Netherlands
diyAudio Member
 
Join Date: Apr 2009
Hi Elias,

I like your approach described here. Could you post a graphic of the special waveform you are using?
  Reply With Quote
Old 18th June 2009, 05:35 AM   #10
diyAudio Member
 
Join Date: Jul 2005
Location: none
I also would love to hear more about how these measurements were done.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Omnipole, monopole, dipole and...nopole?? terry j Multi-Way 25 1st July 2007 03:28 AM
Getting Dipole bass out of a monopole subwoofer Hara Subwoofers 18 14th July 2006 12:55 AM
Dipole vs monopole, balls or not ... ? Jussi Multi-Way 11 4th May 2006 03:38 PM
DBX vs BSS vs 24/96 for Dipole/Monopole combo..... gavinson Multi-Way 0 29th November 2005 12:07 AM
Dipole speaker with monopole rear firing midbass? GuyPanico Multi-Way 4 12th November 2005 02:49 PM


New To Site? Need Help?

All times are GMT. The time now is 10:55 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2